Title:  High performance thermoplastic polyureas via a nonisocyanate route from urea and aliphatic diamines.

Abstract: Polyureas (PUrs) with excellent properties have been applied widely in  many fields. These days attention has been turned to non-isocyanate  routes for PUr preparation due to the toxicity and the high cost of  isocyanates. Urea is a green chemcial which can be either from urine or  from recycled carbon dioxide and ammonia. Here we introduce a urea-based  route to prepare PUrs, by melt polycondensation of urea and  1,10-diaminodecane (DA-10) or/and 1,6-diaminohexane (DA-6) without  catalyst, solvent, and high pressure. It is difficult to synthesize such  thermoplastic PUrs from diisocyanate without any solvent since the  melting point of PUr is normally higher than 170°C at which isocyanate  is able to react with urea group to form biuret. The thermoplastic PUrs  obtained in this study exhibit excellent mechanical and thermal  properties. Furthermore, the properties can be adjusted by changing the  feed ratio of diamines (DA-6/DA-10). The compression-molded PUrs show  even better mechanical properties than ultra-high molecular weight  polyethylene (UHMWPE). The values of Young's modulus, strength at break  and elongation at break are found to be 230–300 MPa, 40–60 MPa and  200%–400%, respectively (except for PUr-6). Therefore, this facile,  non-isocyanate approach provides a viable alternative to the current  industrial process for high-performance PUrs.